# Viewing crash dumps on Windows

### Viewing Java Virtual Machine crash logs

If you are running Micro-Manager in the normal way (with the GUI), the Java Virtual Machine will save a crash log if the whole program crashes. Most of the time, such a crash means that something went wrong in one of the C++ components of Micro-Manager.

JVM crash log files are named hs_err_pid*.log, with the process id of the JVM that crashed, and are placed in the Micro-Manager folder.

Although the JVM normally can catch errors that cause the process to crash (such as access violations (= segmentation faults)), sometimes the memory corruption (or some other condition) resulting from the error is severe enough to cause the JVM’s crash handler to fail or not be executed. In that case, the only way to see what happened (save for running Micro-Manager with a debugger attached) is to have Windows produce crash dumps.

Note that, when the JVM saves a crash log, Micro-Manager’s windows will just disappear, with no error dialog box (as far as Windows is concerned, the program terminated of its own will). When the JVM crash handler fails, you will usually see Windows display a message saying “Java(TM) Platform SE binary has stopped working”.

### Generating Windows application crash dumps

The crash dumps saved by this method are binary files. You need a Microsoft debugger (e.g. windbg.exe) to view them.

Windows crash dumps are disabled by default (to be precise, saving them locally is disabled by default; there is a mechanism to allow sending the dumps to Microsoft, but that is not helpful for our purpose). To enable local saving of crash dumps on Windows Vista, 7, or later, download this file, extract the .reg file, and open it (administrator permission will be required), which will add the necessary settings to the Windows registry. (See Microsoft’s documentation for details on this.)

Following this setup, when java.exe or javaw.exe crashes, a crash dump should be saved at

 %LocalAppData%\CrashDumps\java.exe.*.dmp


or

 %LocalAppData%\CrashDumps\javaw.exe.*.dmp


where the location of %LocalAppData% can be checked by typing echo %LocalAppData% into the Command Prompt. The App Data directory is hidden by default; the easiest way to open the CrashDumps folder is to open a Command Prompt and type

 start %LocalAppData%\CrashDumps


Note that crash dump files can get quite large (especially if the application is using a lot of memory).

This file will disable the saving of all Windows application crash dumps.

If you are running Windows XP, the method described on this page should work.